A fighter pilot in the guns/cannon fight must get his guns to bear on his target by pulling 'lead', which basically is aiming ahead of the target so that when he fires, his ammo reaches the critical point in space just as the target gets there. If he is well practiced a good fighter pilot keeps his E up with airspeed much greater than his target, manipulates the 3 dimensional image of the fight in his head, projects the target movement, to get ample 'lead' on the target, tracks it for a period long enough to make sure the target's flight path is going through his aim point, and goes for a 'flythrough shot', disengage away at full power and preferably climbing to convert kinetic energy into potential energy. That is where excess power and accelleration is advantageous. If the target explodes then the jock swaps to another target or rejoins his flight element to engage more targets or go home. If the target flies on, then the attacker has the option of using his greater energy to advantage for another flythrough shot, or, he can slow down to his 'cornering speed' when in close contact with the target for a steady tracking shot, by sitting behind the target a/c . Cornering speed is considerably slower than maximum speed, and is where the you get the best performance in terms of maximum 'g', max turn rate, and minimum turn radius - and maintain it long enough to get a firing solution. Mind you none of this is easy. The other guy is not just sitting there letting you get a nice sight picture. Most WW2 fighters had a 'corner speed' in the range 160 to 220 knots. The combination of power and high max speed allowed the pilot to keep high E. A high powered engine allowed the pilot to maintain his 'corner speed' in close, because at corner speed the angle of attack is high, the 'g' load high, and therefore drag very high, requiring lots of power. Some folk say that horse racing is the sport of kings, but fighter pilots know what really is the sports of kings!
